use Benchmark(cmpthese);
cmpthese(1000000, {
	'a' => sub {
		$_ = 'this that this those this these.';
		$a = () = /this/g;
	},
	'b' => sub {
		$_ = 'this that this those this these.';
		$a++ while(s/this//);
	},
	'c' => sub {
		$_ = 'this that this those this these.';		
		$a = s/this/this/g;
	}
});

##</code><code>##

      Rate    a    b    c
a 478240/s   --  -4% -19%
b 497018/s   4%   -- -16%
c 588235/s  23%  18%   --